Put packed brown sugar and margarine in pan and brown. Add half cup of water slowly and cook unitl sugar dissolves. In a separate bowl, mix brown sugar, cornstarch and salt. Heat can of evaporated milk. In a separate bowl, mix egg yolks and milk. Add egg/milk mixture to dry ingredient's mixture. Pour hot sugar mixture into heating milk. Add egg mixture. Cook unitl thick. Pour into baked crust. In a separate bowl, make meringue by beating egg whites with an electric mixer. Slowly add sugar. Beat until light and fluffly and stiff peaks form. Top pie filling with meringue and bake until meringue is golden brown.